X-ray screen for taking skiagrams



March 13, 1928.

R. MANNI- X-RAY SCREEN FOR TAKING SKIAGRAIS Fil'ed Dec. 1 2, 1924 B v n for:

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Patented Mar. 13, 1928.

UNITED ("STATES PATENT OFFICE.

Iwnonr MANNL, or KARLSBAD', CZECHOSLOVAKIA.

x-nAY SCREEN ron TAKING SKIAGRAMS.-

Application filed December 12, 1924, Serial No. 755,427, and in Czechoslovakia December 24, 1923. g

This invention relates to those screens for taking skiagrams which are placed between the illuminated body and the light screen or the photographic plate and has for its objcct to prevent so far as possible the socalled lateral secondary radiation of the body which obscures the picture.

The invention is applied to a known screen which consists of a star formed of one or more plates and according to this invention the screen is so constructed that not only does the middle point of the plate system (which forms a disturbing factor for the picture) fall outside the light shield but the convergence of the individual sectors is so small that it produces no disturbing action. A screen so constructed will there fore act in a similar manner throughout its entire surface, i. e. any portion of it prevents secondary radiation.

The invention is illustrated in the accompanying drawings, in which Figure 1 is a front elevation of the screen where the I source of light (the focus) is supposed to lie of the old type and Figure 4 is a diagram matic view illustrating the development of the new screen and showing the latter in use.

A conventional screen, as shown in Figure 3, has the various plates intersecting in a common intersection point 3, at the middle of the screen 2.

According to this invention the screen 2 has convergent plates directed to an intersection point 3 lying outside the screen 2, said point 3 being the center of curvature of the are 1. Thus the intersection point, which has caused difliculty heretofore, is eliminated.

A screen so constructed would not, however, eliminate the defect that the centering of the natural axis of the screen is not absolute (i. e. there is no perpendicular pass ing through the middle point of the screen but only through the axis of the plate system running parallel to it). When the screen is in use it is given an apparently unnatural angle of inclination with respect to the object. This angle of inclination would result in either rendering the picture projected on the light screen or on the photographic plate out of focus or it would cause when corrected by turning the projection surface to a corresponding extent an undesirable enlargement and cut olf light from the picture. Instead of correcting the inclination of the screen by turning the plate of projection the eccentric portion of the screen is inclined to the axis of the wheel at the same angle which this makes with the horizontals (to the useful rays). An X ray screen in accordance with this invention is therefore not only an eccentric sector cut from animaginary wheel whose spokes are plates, but a. sector inclined to the axis of the wheel.

The following results The plates 2 converge not only to the point 3 but also to a point 4 (Fig. 2) of the horizontal upon the desired axis of the screen 2 at the focus 5 (Figure 4). A double convergence of the plates is thus obtained, one to the point 3 and one to they point 4 coinciding, for example, with the focus. The last said convergence obviates the necessity of giving an undesirable inclination to the screen.

By not inclining the screen the advan only a small adjustment so that the instru ment will also require only a small angle of inclination.

Referring to Figure l, it can be seen that the screen of the present invention is, in effect a section cutout of a large circle having plates for radii, said section not including the center of the circle. The circle 5 has plates 6 radiating from the center 3, in the same way as shown in Figure 3. The screen ofthe present invention, however, is only a partof the large circle or screen 5, being the part shown at 2 in solid lines. Thus it can be seen that the plates 4t of the screen have a common center 3 outside the limits of the screen 2. At the left side of Figure 4, the screen is shown in use, the objective being placed between the screen 2 and the Xray source 5.

What I claim is 1. An X-ray screen adapted to prevent lateral secondary radiation, having plates extending across the screen and all converging toward a common intersection point; disposed outside the screen and in the plane of its working surface.

2. The combination with a source of X- rays, of an X-ray screen adapted to prevent lateral secondary radiation, said screen having plates extending across the screen and all converging toward a common intersection point disposed outside the screen and in the plane of its working surface, said screen being adapted, when in use, to be disposed in a plane. which is oblique to a straight line connecting said intersection point and the source of the X-rays.

In testimony whereof I allix my signature.

RUDOLF MANNL. 

